1. Field of the Invention
The present invention relates to a method of manufacturing a photovoltaic device. More specifically, the present invention relates to a method of manufacturing a photovoltaic device wherein a plurality of photoelectric converting regions are formed on the substrate and respective photoelectric converting regions are connected in a series fashion.
2. Description of the Prior Art
Conventionally, the photovoltaic device is known wherein a plurality of photoelectric converting regions are formed on one substrate and these photoelectric converting regions are electrically connected in a series fashion. One example of such a photovoltaic device is, for example, disclosed in the U.S. Pat. No. 4,281,208, patented on July 28, 1981, the U.S. Pat. No. 4,292,092, patented on Sept. 29, 1981, and so on.
FIG. 1 is a perspective view of the major part showing an example of a photovoltaic device being the background of the present invention. The structure of the photovoltaic device as shown in FIG. 1 is disclosed also in two U.S. patents as cited above. This photovoltaic device comprises a glass substrate 10, and on the glass substrate 10, a plurality of (three in the illustrated example) photoelectric converting regions 14a, 14b and 14c are formed. First electrode film parts, that is, transparent conductive film parts 11a, 11b and 11c are formed corresponding to these photoelectric converting regions 14a, 14b and 14c, respectively. Semiconductor film parts 12a, 12b and 12c comprising amorphous silicon are formed on respective transparent conductive film parts 11a, 11b and 11c. Respective semiconductor film parts 12a, 12b and 12c contain a PIN junction which is parallel to the film surface. Respective end portions 11a', 11b' and 11c' of the transparent conductive film parts 11a, 11b and 11c of respective photoelectric converting regions 14a, 14b and 14c are exposed beyond the end portions of the semiconductor film parts 12a, 12b and 12c in the longitudinal direction of the substrate 10. Then, on the semiconductor film parts 12a, 12b and 12c, second electrode film parts, that is, back electrode film parts 13a, 13b and 13c are formed, respectively. Respective end portions 13a' and 13b' of these back electrode film parts 13a and 13b are connected to the exposed transparent conductive film parts 11b' and 11c' of adjacent photoelectric converting regions, respectively. When the light impinges through the glass substrate 10 and the transparent conductive film parts 11a, 11b and 11c, respective semiconductor film parts 12a, 12b and 12c generate photoelectromotive forces, respectively. The photoelectromotive forces generated by respective semiconductor film parts 12a, 12b and 12c are taken out between the transparent conductive film part 11a and the back electrode film part 13c in a series fashion, that is, in a cumulative fashion.
In the photovoltaic device as shown in FIG. 1, to obtain a higher energy efficiency, the light utilization rate must be made larger. That is, the effective area of the semiconductor film part actually contributing to power generation is to be made larger. It is known as is disclosed in the U.S. Pat. No. 4,292,092 cited above that for the purpose of enlarging the effective area as described above, a transparent conductive film formed on the glass substrate is divided into transparent conductive film parts corresponding to respective photoelectric converting regions by irradiating a laser beam.
FIG. 2 is a view showing an example of the pattern of the transparent conductive film parts of the photovoltaic device as shown in FIG. 1. The transparent conductive film formed on the one main surface of the glass substrate 10 in a substantially entire fashion is removed by irradiating a laser beam to form spaces 7, 7, . . . . By these spaces 7, 7, . . . , the transparent conductive film is divided into parts corresponding to respective photoelectric converting regions 14a, 14b and 14c. Then, as shown in FIG. 1, the semiconductor film parts 12a, 12b and 12c and the back electrode film parts 13a, 13b and 13c are formed in sequence. In the photovoltaic device thus completed, the spaces 7 between respective photoelectric converting regions 14a, 14b and 14c can be made small, and thereby the desired end of increasing the effective area actually contributing to power generation can be attained. However, the results of the experiments conducted by the present inventors were such that respective first and second electrode film parts of the photoelectric converting regions 14a, 14b and 14c came in contact with each other for some reason, and as a result an accident of short-circuit in the photoelectric converting region took place. An occurrence of such a short-circuit accident reduces the yield rate of manufacturing of the photovoltaic device, and consequently causes a reduction in quality and a rise in cost thereof.